Distance and speed indicating system



May 12, 1953 G. GUANELLA DISTANCE AND SPEED INDICATING SYSTEM 2Sheets-Sheet l Filed Sept. 22, 1948 INVENTOR -HEP May 12, 1953 G.GUANELLA 2,638,586

DISTANCE AND SPEED INDICATING SYSTEM Filed sept. 22. 1948 2 Sheets-Sheet2 INVENTOR Gas 7W Guy/vean ATTORNEY Patented May 12, 1953 3sat DISTANCEAND SPEED INDICATING SYSTEM Application September 22, lill-i8, SerialNo. 50,520 In Switzerland 'October' 27, 1943 section 1, rubric Law@desgaste-1946 Patent expires October 27, 1963 l Claims.

rlhis application is a continuation-in-part of application Serial lNo.578,013, led February 15, 1945, entitled Dista-nce and Speed indicatingSystem, now Patent 2,45i,822, dated October i9, 1948.

The present invention relates to a system, for indicating the distanceand/or speed of moving objects such as aircraft or the like by means ofradiant energy, in particular high frequency radio waves. Moreparticularly, the invention is concerned With an improved method of andarrangement for determining the distance o a moving object independentlyof its speed in a direction towards and away irom the observer.

Methods of determining distance by means of acoustic or electromagneticoscillations according to the echo or reiecticn principle are Wellknown, wherein the transmitted frequency is varied periodically and abeat is produced between a portion of the radiated oscillation energyand the oscillation reflected from the object whose distance is to bedetermined, said beat having a frequency proportional to the distance.

A disadvantage of these methods is due to the fact that a relativemovement of the body, in the direction to or from the observer, willcause an increase or decrease ci the beat frequency due to the so-calledDoppler effect. As a result there will be an error in the distancedetermined from the beat frequency which may be substantial in case offast moving objects, such as air craft. A further disadvantage of knownsystems is due to the fact that the speed ci the reilecting object whichit is desirable to know in many cases cannot be determined directly froma measurement 0f this type.

In order to overcome the above drawback and other detects inherent inthe known systems, the present invention has for its object theprovision of means for and a method of separately or simultaneouslydetermining distance and velocity ci a moving object by means of radiantwave energy, according to which the electrical oscillations 0i atransmitter having its frequency modulated in a predetermined manner areapplied to at least one receiver, said oscillations being transmitted inpart directly from the transmitter and in part by way of the reflectingobject, Whose distance and/or speed it is desired to determine.

W ith the above and further objects in view, as will appear hereafter,the invention is charac terized by a specic modulation of the frequencyof the transmitted oscillation energy in such a manner as to produce acomposite beat frequency 2 by supeimposin'g the reflected and thedirectly transmittedoscillations, the desired distance and speed beingderived 'from the respective components of the beat frequency energywhich are dependent uponor proportional to the distance and speed of theobject, `i'esr'iectively.

Among the advantages of the invention is 'the fact that distance andrelative speed 'may be indicated continuously and that the operation ofthe apparatus 'for carrying the linvention into e'iect is extremelysimple.

The invention, both 'as to its further objects and novel aspects, will'become more apparent from the following 'detailed description 'of a'few practical embodiments, with reference to the acccmpanyingdrawingsformi-ng part of this specification, and wherein;

Figure 1 is a block diagram of a basic 'distance and speed indicatingsystem constructed in accordance with the principles of the invention;

`Figure 2 *is a graph'showing the special Wave shape for varying thetransmitting frequency eniplo'ye'd by the invention;

Figul is a blckdiag'rain illustrating a modified system 'fr carrying outthe invention;

Figure 4 shows a'ie'quency Yindicating scale explanatory of 'the'function and operation of Figur'e 3;

Figures 5 and .6 are iblock diagrams showing still further modiicatiohsof the invention; and

Figure i? is a "incre detailed circuit diagram of ra distance and 'speedindicating system according to the invention as shown in Figure l.

Like reference characters 'identify like parts throughout thel differentviews 'of the drawings.

Referring to Figure 1, there is shown a transmitter S adapted toYrf'idiate a high frequency signal eis preferably in the form of anarrow or concentrated beam, said signal having a frequency fis which isvaried continuously and periodically according to a triangular wave byalternately increasing and decreasing the transmitn ting frequencyatsubstantially equal rates between upper and lower limits in the mannershown by the curve fis in rFigure 2. The transmitted signal, afterreflection by a remote object whose distance and/or speed is to bedetermined, is intercepted by a suitable receiver E mounted close to orcombined With the transmitter S, said receiver including the usual meansfor amplifying and rectifyng the received signal energy. There isfurthermore 'app-lied to the receiver E a portion 'of the sign'z'ilv eisd'i'rectly'from the transmitter and coinbined or superimposed upon thesignal ezs received by way of reflection from the distant object. As aresult, a difference frequency or beat signal es will be produced in theoutput of the receiver E the frequency of which varies in directproportionto the distance of the reflecting object, in a manner wellknown in connection with frequency modulated type distance determinationsystems of this general character.

Referring more specifically to Figure 2, the triangular curve f1s, aspointedfout,represents the variation of the transmitted frequencyrg as afunction of time t, curve f2s represents the frequency of the receivedsignalezseafter-.travelling to and from the 'distant object, curvefesrtbemg displaced in frequency relative to curve fis by a frequencydifference Fe which is -proportionalfto the distance of the object in amannerwell 'understood, assuming the ob-ject to be stationaryor at restrelative to the transmitter S. As a result,

the receiver output `or beat frequencyignal es will have afrequencywhichvaries, in-fproportion to the distance of theyremoteobject toybedetermined, which beat frequency.maybemeasured or translated in anysuitable manner fol` effecting an indication or direct reading distanceydetermi,- nation.

Assumingnow that .theobject is movingat a speed 'U in a directiontowards or away4 from the transmitter S, an additional change .of the*frequency of the reflected and receivedsignal c25 will Voccur due to the.well known Doppler effect, said additional'frequencychange or 'Dopplerfre.- quency being directly `proportional tothe speed o and resultinginl'a decrease or increase of the signal frequency, depending' uponwhetherV the object recedes from or approaches the transmitter,respectively. Asa result, curve lfzs representing the actual frequencyatthe receiver input will be further displacedrelativerrjtol curve fisby an amount Fv equalto Ythe Doppler frequency and being proportionaltothe relative'speed ubetween the object and the transniittefr..3:'E [he`resultant total frequencychanges Fis-fand F-'scfonfboth increasing anddecreasing "transmitting frequency, and as shown inlFigure 2`will'therefo're be equal to the sum or difference,l respectively, ofthe difference or beat frequencies Fd and Fv inthe case of an obj ectwhich moves in a direction away from the transmitter at 4a `speed o. Ifthe object moves in a direction towards the transmitter, vthe values ofF's and F"S4 will*'be'."interchangedfor increasing and decreasingtransmitting frequency, as is readily understood. v In accordance withthe foregoing, the frequency Fs of the rectified beat voltage 'es at the'output of the receiver E varies between the following values:F's:(Fd-{Fv) and Fs;f(E'd;Fv) v'as shown and readily understood fromthediagram of Figure 2'. I

' By means of suitable networks o r retardation devices N1 and N2,Figure Lthe alternately and successively occurring beat frequencyAsignals of frequency Fs and F"s are retarded by 1 1nequa1 amounts insuch a manner that they will occur simultaneously or substantiallycoincide with each other at the outputs ofthe networks. In other words,the relative retardation or time displacement of the output signals bythe delay devices N1 and N2 should be one-half of the modulating orfrequency variation periods of the transmitted signals, in order toeiect a coincidence of the sum and diierence frequency signals Fs andFs. By then forming the, modulation Cil 4 product of the relativelyretarded voltages in a modulator M, a resultant voltage em is obtainedincluding the following sum and difference frequencies:

F'si-E'fsfzra .l n lF's--F'.s- SZFu rAccQrdingly, thersunfifrequencyF's-l-FG is proportional to the"'distance d and the difference...frequency fFfs-Fq ,is proportional to the speed ,jgrfbesefsumandbdifference frequencies are devf@1.1'111-1'I1cd ormeasuredseparately by means of Vfrequency metersl or indicators Zd and Zvrespecsuitably Calibrating these indicators, indication of the speedand/or actual vadistance, isenabled in a most simple and ecientunanner.Y

gl,rriqclifled arrangement according to the inventi'on is shown inFigures 3 and 4. The rectified receiver output signal eaagain includesthe alternately. and successively .occurring .frequencies components FSland 'Ffsin the manner described hereinabove. There isprovided accordingtokthis embodiment a variable frequency oscillator Ov producing anauxiliary oscillation eg. In..the modulator` M, -theA oscillations esandeg are combin'ed lto produce a -modulation product en which, as shownin Figure 4, comprises the sum and difference frequencies F4 and Fa:equalto F's-i-Fg and Fs-Fg, on the one hand,V andFz. and F1 equal toFfs-l-Fg and Bmw-Fg, on the other hand.

By Ameans ofthe networks N1 and N2, the signalsv ilcation` inthe rectierG, anew difference fre' quency signal er is producedhaving a frequencyF1- which is indicated by a suitableinstrument Z0. In operation,r thefrequency of er. is reduced to zero' by. means of a correspondingadjustment of-thefrequency of oscillator Ov. Accordingly, frequencies F2and'Fa will be equal or coincide with each other.` In. the latter case,.the auxiliary frequency Fgof oscillator -Ov will be proportional to the1frequencyFv .or in turn to the speed .'v, since (F'sTFf's) :2Fvaccording tothe foregoing. Thus, if theoscillator Oy is, suitablycalibrated, tliejspeed .may be determined directly from the oscillatoradjustment.4 Furthermore, the frequenciesFaand F3 whichin this case areequal and coincide with Fd, may be indicated by the frequency indicatorZd which thus enables a direct indication of the distance d.

Figure 5 shows a further modifcationof a system for carryinginto effectthe invention. The beat frequencyvoltage es yobtained from the receiver,E is intermodulated in a first modulator M1 with the auxiliarymodulating signal eh of constant frequency Fhand produced by anoscillator O11, lwhereby to result in a voltage e1 comprising the sumfrequency Fs--Fh. By means of a further modulation in avsecond modulatorM2 with'v the auxiliary modulating signal ed having an adjustablefrequency F'd and produced by an oscillator Od, there is obtained afurther difference frequency signal, e2 having a frequency Fs-i-Fh-Fd.The total displacement Fn-F'a of the beat frequency Fs can accordinglybe controlled by adjusting the oscillator Od. By means of a furthermodulator M3, the modulation product es of signal e2 and a furtheradjustable auxiliary-frequency Fv producedv by an oscillator Ov isobtained, the signal e3 comprising the following sum and differencefrequency components:

With increasing transmitting frequency and increasing distance thissignal contains the following components:

With decreasing transmitting frequency, however, Fa contains thefollowing components:

These two components are rendered Visible in the frequency spectrographK1 in the form of corresponding scale deflections. Generator Ov is thenadjusted in such a manner that both deflections coincide7 that is, thatF3=F"a. In this case, (Fv-F) =0, that is the auxiliary frequency Fvadjusted by means of Ov coincides with the beat frequency portion FVwhich is proportional to the speed of the object. The speed mayaccordingly be read directly from the setting of the oscillator Ov bysuitably calibrating the latter. After this adjustment, the indicationof the coinciding frequencies Fa and F3 in the frequency spectrograph isbrought into the middle of the scale by adjusting the auxiliaryfrequency Fa of the oscillator Oe. This setting corresponds to thefrequency Fh of the oscillator O11. Accordingly, Fd-Fd=0, that is theauxiliary frequency F'd coincides with the portion Fd of the beatfrequency which is proportional to the distance d. By suitablyCalibrating the oscillator Od, it is thus possible to obtain a directindication of the actual distance of the object free from any error dueto the Doppler eiect.

In order to enable a more accurate adjustment and measurement, a secondfrequency indicator K2 may be provided following the first indicator K1,by means of which small deviations from frequency Fh may be clearlydetermined. This frequency indicator may be a frequency spectrographprovided with smaller spacings between the frequency calibrations or itmay be a frequency discriminator capable of indicating deviations fromthe prescribed frequency both as regards magnitude and sign. Suchfrequency discriminators, which may comprise a pair of coupledoscillation circuits and means for effecting a phase comparison betweenthe input and output Voltages of said circuits or which may comprise twomutually detuned oscillation circuits and means for effecting anamplitude comparison of both output voltages of said circuits, have theadvanthat disturbing voltages such as amplifier noise do not cause apermanent deflection, since the disturbing frequencies lie both a'boveand below the prescribed frequency and on the average their effects willcancel each other. Small differences between the alternately occurringfrequencies Fa and F3 can furthermore be determined by rectification ofthe signals in G and indicating the resulting beat by a frequencyindicator Zo. For this purpose. networks N1, N2 are provided havingunequal transit times so as to cause the alternately occurringfrequencies to coincide in time.

In practice, the average frequency of K1 and K2, respectively, maydiffer from the auxiliary frequency Fh of oscillator Oh. In this case,the auxiliary frequency F'd after adjustment to the middle of the scalealso deviates by a corresponding amount from the frequency Fdproportional to the distance, which fact can readily be taken 6 intoaccount by suitably calibrating the oscillator Od.

A somewhat modified arrangement similar to Figure 5 is shown in Figure6. In the latter, the output of modulator M4 supplies a signal e4 havinga frequency F4=FS+F1 In the modulators M5 and M6, the differencefrequencies are formed between the signal e4 and the auxiliaryfrequencies F's and FWS produced by the oscillators Os and O"s,respectively. The resulting frequencies F5 and Fs of the output signalse5 and es of the modulators then contain the following componentst Boththese components are caused to coincide by adjusting the oscillators O'sand O"s. Accordlngly:

The deflections of K5 and Ks are then brought to the mid-point of thescale corresponding to a frequency Fn, by means of a furthersimultaneous adjustment of Os, Os. Accordingly:

F"e=Fh-l-Fa-Fv-Fs=F/ From this the sum and difference of F5 and Fe isobtained as follows:

By a suitable calibration, it is possible, therefore, to obtain a directindication of the distance d from the sum of the settings of theoscillators Os and Os and to obtain an indication of the relative speedu from the difference of said settings. To facilitate the reading, twoscales may be provided which are connected with the adjusting elementsof the oscillators by means of differential gear arrangement adapted toform the sum and difference values indicated by suitable scales whichthus enable a direct indication of the sum and diiference of bothsettings and accordingly of the distance and speed, respectively, to bedetermined. For Fk=F/L, the expression Fd is simplified accordingly asfollows:

To enable the required average frequency Fk to be more accuratelyindicated, discriminators D5, De may be provided with meters Z5 and Z6which serve to indicate small deviations in magnitude and sign from. therequired frequency Fk.

With the arrangements described, it is possible to automatically adjustthe auxiliary oscillators to correspond to a variable distance andvelocity. The discriminator output voltage D5 may for instance servefor` the automatic adjustment of the oscillator O's, so that thisoscillator may be continuously controlled to maintain the frequency Fkconstant. It is also possible in a similar manner to automaticallyreadjust oscillator O' 5 in dependence on the output voltage of De.

Auxiliary oscillators Oh in Figures 5 and 6 may also be constructed soas to be capable of being adjusted in steps for changing the distan-cerange covered by the system.

The distance determined by measuring the beat frequency depends on thewobbling frequency and the range Within which the frequency oftransmitter S is varied. As a result of changes aces-gocce@ intheiwobblingispeedoii frequency' range@ meastss.. uring errors mayoccur. It is therefore advisable: f. to test"thetadjustmentictthetsystemiby connes ing .es calibrating'line L=Havingfar known transit.` en. time*hetwe'enitheA transmitter- 'S.andntliemeceiver 11H5 E as shoWnn'. Figiire.- .The wobblingftrequency1.x" of thettransnnttennis' then :so adjustethat thei is# distancezindication: :corresponds with?. the@ 'transit v timeof line-Lei. n

The lz'frequency-.1 of thee .fielectricallf oscillations .-:10employed.7 isi generallylhig'hen :than i100 tnc.',z.thei1mostnfavorable'freduency' to beselected in eachcase depending on thesize and shape of the re. ecting object. i

Referring to Figure 7, there is shown a more'isI detailed circuitdiagram of a:distance1indicating system .accordingtg Figurel.,

The .transmitterf'llr 'comprisesrdn thejexample shown, a vacuum tubeoscillator' in the form 'of 1- a triode` V1 havingi.associatedctherewitha re 20 generative or feed-back circuit 'of standard; construction vwellknown in the. art. Thetun'ing condenser of the oscillating"'or 'tankcircuit of the generatoreis'shunted by an .additional-a rotary;.;:'

tuning condenser-@G1 Whichiis. driven continuously 'a 2.54

by at rnotor-I Me rior: modulaizi'ng-zthev transmitting. :f frequencyinthemannera's show-nain FigureY 2-.= .f For this purposer thaccndenserC1, in the example illustrated, 'comprises'astator'in the form of a rstpair of spacedfand ifixedwsemidfcircular 30 plates'orelectrodesarrangednin ai: single .planefnlz and constituting thearmatures :of tliecondenserze' connected in parallelto the-oscillator.tank circuit, in the manner shown 'in the drawing. The rotor comprisesa pair 'of .sim-ila1- :semicircular 35 electrodesinsulatedlyconnectedwitheac-h other.` and :concentricallyimounted to thelouteror sta-.Ationaryi electrodes. .ln an arrangement. .of this type, ,the. totalcapacity... between. the...stationar.y electrodes varies- ..betwe'en.,zero.. .,(axesaofi `both ..40 electrode pair in parallelianda maximumy.(axes.. of both. electrode-.pairs-.lat rightjangle). accord.- ing to.a:linear..sawetooth,..wave,v in. the manner. shown in Eigure2..

The" .receiver .Re advantageouslyD .includeslf a similaltuning.condenser' Cz alsofdriven by .tha motor'lMQfin su-chwamanner asto-.rvarythemeceiverY tuning. adjustment.. in synchronism .or cor,.. irespondan'ce.-yvith'the.;yariations of the. trans-1.... mitted'frequency. In thisllr'nanneigA itis.. possible..50 to use a sharplytuned receiver to'- eliminate noise and other interferenceas Wilb bereadily understood It is possible, however, to omitthe tum ingcondenser-'Cz and'to utilize a5 receiver of suit''' ableland width'i The`trahsmittedi--\high^'freduency oscillations are applied to the''rece-iverrReL'in partl directly* (oscillatoiis'emf and' in*part'findire'ctly =by Way of" reflection-imma '.distantobject 'and'with'a' 'time delay' vlceiilgproportioifiate"to the.I oloj ectrdistance` "60(oscillationsA ezel". fr' Both'- received signalf=voltages""' being'-superimposed'lin the receiver-"aresrectie'cl 'i by means- 'ofrectierfDefof fany *known type-' 'v whereby-- to 'res-ult alow-frec1uencyl voltagef'" havinga/ freduencyi#corresponding yto 4thebeat''6'5 frequency Fg' between the' signals 'en and enf-Thisbeat`frequency; Whichf'according-to 'the' 'above' varies periodically'between' two" values propor' tional, respectivelyfto the sumandto' thediffer' ence'of thedistance' and speed of theremote. ob- "70 ject, isfurthermore amplified by 'means of ailow., frequency amplifier."comprising'. .a pair. of resist..` 1- ance coupledamplifier tubes-...V2andisin the. exampleshown in the; drawing. the ampliedybeat.-frequency...voltage.es are ..ap...

Components .of .j

puedas. the-.neiayzeevic slm enana. efrne"1atter;=.=-

lbasisiof in the example 'shovv-rigav operateaon :the magnetic recordingand. iieproduction-by the provision of endlessHmagneticarecording. wiresor tapes B1 and B2 with associate recording heads or magnets Si.andi-isa', pickLuD-jheadsAi and and "erasingior quenching 'heads L1 and-"Lz, fre-'f spectively. IThe recording heads S1 andl Si serve" to recordthe.. beat.7 evoltage; .signal .components upon the record carriers1 andB2 .which .are

movedat a" constant speedily "the"'fprovision" of suitable driving;means, "such' 'as electric''notors or the like. After-recordingthe.signals'are reproducedby means of the pick-up or reproducing..

heads A1 and A2 andsubse'quently'are .removed or erasediby-lneans 'ofthe quenching'heads L1 andLLa. respectively. ,The reproduced vsignalsare amplified'by means ,of suitablelampliflersas shoe/nat vd. and v5..".Tnede1ayzpericds-may-be1 adjustedby suitablyv designing'the.'distances d1 'andfffz between .the 'recording'.'and vpick-up heads;For' practical. ,.purposes, a, single delay'.

since'thedistance indication is dependent upon... delay periods one. .ofwhich'may'be equal' to' zero: NIn the' present"case,...'.

the difference between' the two 'delay devices have been shown in orderto equalize-.or balance the` .transmission .conditions in both'receivingchannels.l 1in particular any. .ad'

Aditional'phase'rotationc'aused'as a result. of the' recording'andreproduction" operations..

The "mutually delayed" signals are" `appliedto x the modulatpnM'productvthereof.- Thev 'modulator'. shown 'known as airing modulatorcomprises four' rectifiers, D1',

for forming of 'the modulation D2, D3 and D4 conn'ected'iri serieswith'the input' 1' and output circuits connected' in' standard fashion'asv sho wn.

The" output vsignal' em'of the' modulatorl M which'in a' knownmanner'contains both 'Sum" and difference frequencymomponents.. of theap.

plied 'input'signals is in turn'appliedto both the speed'and `distance'indicating' vdevices Zt and Zd,

respectively: ."Devices' Zv' and Za includesluitable 'f band'pass-filters" BPI "and "BPZ for segregating' the respective signalfrequencies; .The `segregated i sum and difference" frequencies are`applied. .to

suitable"amplitude'limiters 'or clipper circuitsin l the forin'ofrectiner's'Ds and Ds Vconnected' in seriesi-withf'suit'ab'le .voltageSources such. as bat' teries'"Q1 andQg; respectively. These limiters'functionin awell known manner; in that as' soonv as the' low frequency'amplitudeexceeds the value1' of the"respective""natteryl voltage by aslight amount;-lcurrentwillpass through the rectifier whereby'to'prevent'a further.' amplitude increase. Th'amplitudelimited currents'are applied .to

suitableconverting"devices'or lfrequency .detectors 'consisting in theexample','shownof simple,

slope filters; in the""form"of condensers...C5 'and Cv,theicurrentthrough lwhich yaries in ampli: tude' 'in accordance withvthe frequency in 'the manner' well '-unders'too'd; 'After 'subsequentrec.-

.obtained in this'manner a' pair of output cur-.j

ergize theinstru'mentslv and la which. latter may.

be directly 'calibrated in relativespeed and distance.units......

As will be understood,-.any .othe'ntype of fre.'- ...f

quencydetectonor indicatonsuchf as arequency.-

analyzer...comprising^.atpluralityof mechanicabor.

electrical resonant units may be employed for the purpose of theinvention in place of the specic frequency indicator shown in thedrawing. Furthermore the delay devices N1 and N2 may be of any otherwell known type, such as in the form of acoustic delay systems orelectrical transmission or artificial delay lines or equivalentelectrical means suitable where extremely high transmitting frequenciesare used for the distance and speed indication.

While there have been shown and described a few desirable embodiments ofthe invention, it will be understood that modifications and variationsas well as the substitution of equivalent parts and circuits for thoseshown herein may be made in accordance with the broader scope and spiritof the invention as defined in the appended claims. The specificationand drawing are, accordingly to be regarded in an illustrative ratherthan a limiting sense.

I claim:

1. In a distance determining system, the combination which comprises asource of high-frequency waves, means for cyclically frequencymodulatingsaid source with the frequency thereof increasing and decreasingalternately at substantially equal rates, a transmitter for radiatingthe frequency-modulated waves towards a distant object, means forreceiving and heterodyning the transmitted waves after reflection fromsaid object with wave energy supplied directly from said source, toproduce beat energies having a frequency varying alternately inaccordance with the sum and difference, respectively, of the distanceand speed of said object with respect to said transmitter due to Dopplereffect, means for deriving a pair of beat energies from saidheterodyning means and for relatively timedelaying said beat energies,and intermodulating means energized by both said beat energies.

2. In a distance measuring system as claimed in claim 1, a frequencyindicator connected to the output of said modulating means andresponsive to the frequency component proportional to the distance ofsaid object.

3. In a distance determining system, the combination which comprises asource of radio waves, means for cyclically frequency-modulating saidsource according to a triangular pattern with the frequency of said wavealternately increasing and decreasing linearly at substantially equalrates, a transmitter for radiating the modulated waves towards a distantobject, means for receiving said waves after reflection by said objectand hetercdyning the received waves with wave r energy directly derivedfrom the transmitter, to produce beat energies having a frequencyvarying alternately according to the sum and difference, respectively,of the distance and speed of said object with respect to saidtransmitter, means co for deriving a pair of beat energies from saidheterodyning means and for relatively time-delaying of the derivedenergies, and intermodulating means energized by both said beatenergles.

4. In a distance measuring system as claimed in claim 3, a frequencyindicator connected to said modulating means and responsive to thefrequency component proportional to the absolute distance of saidobject.

In a distance measuring system as claimed in claim 3, a pair offrequency indicating means connected to the output of said modulatingmeans and responsive, respectively, to the frequency componentsproportional to the absolute distance and relative speed of said object.

6. In a radio distance determining device comprising a transmitter foremitting radio waves having a frequency increasing and decreasingalternately at substantially equal rates, means for receiving said wavesafter reflection by a distant object and for combining the receivedwaves with waves directly supplied by said transmitter, to produce abeat signal, a pair of beat signal branch circuits, connected to saidreceiving means, means for relatively time delaying the signals throughsaid branch circuits, and means for mutually intermodulating the outputsignals of said branch circuits.

7. In a radio distance determining device comprising a transmitter foremitting radio waves hair'ng a frequency increasing and decreasingperiodically and linearly at equal rates according to a triangularpattern, means for receiving said waves after refiection by a distantobject and for combining the received waves with wave energy directlysupplied by said transmitter, to produce a beat signal, a pair of beatsignal branch circuits connected to said receiving means,

y means for relatively time delaying the signals through said branchcircuits by a period equal to one-half of the frequency variation cyclesof the emitted waves, and means for mutually intermodulating the outputsignals of said branch circuits.

GUSTAV GUANELLA.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 2,268,587 Guanella Jan. 6, 1942 2,422,135 Sanders June 10,1947 2,424,263 Woodyard July 22, 1947 2,467,455 Aurell Apr. 19, 19492,546,973 Chatterjea et al. Apr. 3, 1951 2,556,109 Rust et al. June 5,1951 FOREIGN PATENTS Number Country Date 241,443 Switzerland Aug. 1,1946

